(1) Field of the Invention
The present invention relates to an observation unit. More specifically, the present invention relates to an observation unit with which the inside of a reaction chamber of a semiconductor manufacturing apparatus in an atmosphere of a high temperature can be observed.
(2) Description of Related Art
A vapor phase epitaxial growth system to be used for manufacturing a semiconductor is an apparatus in which a semiconductor substrate is placed on a susceptor disposed inside a reaction chamber of the apparatus and a reactive gas containing a source gas of SiHCl3, etc., and a carrier gas of hydrogen, etc., is supplied to the inside of the reaction chamber and the semiconductor substrate is heated to deposit and grow silicon single crystal on the semiconductor substrate.
By this heating in a vapor phase epitaxial growth system, the inside of the reaction chamber reaches an atmosphere of a high temperature of about 1100° C., and on the other hand, due to this high temperature heating, deformation such as warping of the semiconductor substrate occurs, and if the epitaxial crystal growth reaction is continued with this deformation left, an undesired epitaxial layer is formed on the back side of the semiconductor substrate.
To investigate whether such an undesired epitaxial layer has been formed, it is considered that the semiconductor substrate is taken out from the reaction chamber after the epitaxial crystal growth reaction ends and investigation as to whether the semiconductor substrate has deformation such as warping is made by visually checking it, however, when the semiconductor substrate is taken out, such deformation may have been restored, and it is difficult to judge whether deformation had been occurred during the epitaxial crystal growth reaction.
Concerning the inside of the reaction chamber, it has been demanded to observe the state and situation of the inside of the reaction chamber during the epitaxial crystal growth reaction to check a phenomenon in which the semiconductor substrate is displaced from a predetermined position on the susceptor which the semiconductor substrate is placed on and a phenomenon in which the semiconductor substrate is damaged. Coating on a quartz dome forming the reaction chamber has great influence on the epitaxial crystal growth reaction, and it has also been demanded to observe the quartz dome.
As an apparatus for observing the inside of the chamber in an atmosphere of a high temperature, for example, Japanese Patent No. 2891672 describes an image taking part 101 of a high-temperature atmosphere furnace interior observation unit including an outer cylinder 102 formed in a cylindrical shape, a first inner cylinder 103 disposed inside this outer cylinder 102 and formed into a length which makes its tip end slightly higher than a tip end of the outer cylinder 102, a second inner cylinder 104 disposed inside this first inner cylinder 103 and whose tip end is extended to the same position as the tip end of the outer cylinder 102, a ring-shaped closing plate 105 which closes the tip end sides of the second inner cylinder 104 and the outer cylinder 102, a third inner cylinder 106 disposed inside the second inner cylinder 104, a heat ray cut filter 108 which is disposed at the tip end portion of the third inner cylinder 106, takes-in an optical image from a monitor window 107 formed at a central portion of the closing plate 105 and transmits only visible light components while cutting heat ray components, a CCD camera 109 which is disposed above the heat ray cut filter 108 inside the third inner cylinder 106 and converts the optical image (visible light image) transmitted through the heat ray cut filter into an electrical signal (video signal) and supplies it to an upper part, a pipe 110 forming a spiral flow channel 111 by spirally partitioning a cylindrical space formed between the first inner cylinder 103 and the second inner cylinder 104, and a thermocouple 112 which is disposed near the CCD camera 109 and measures the temperature of this CCD camera 109 portion and supplies the result of measurement to the upper part via a compensating lead wire 113.
With this constitution, it becomes possible to continuously observe the state of the inside of a furnace in a high-temperature atmosphere such as an electric furnace or a coke oven while efficiently cooling the image taking part, the heat ray cut filter, and the CCD camera, etc. FIG. 3 is a schematic view of the image taking part of the conventional high-temperature atmosphere furnace interior observation unit.